A type of spread spectrum method utilizing a direct spread technique. Data signals are spread over a wide frequency band at low power. By continuing to browse this website without changing your web-browser cookie settings, you are agreeing to our use of cookies.
Please use latest browser to ensure the best performance on ROHM website. Rohm Breadcrumb. Analog modulation is typically used for AM, FM radio, and short-wave broadcasting. Digital modulation involves transmission of binary signals 0 and 1. Modulation Method Definitions In wireless communication, information is transmitted by encoding voice and data on radio waves of certain frequencies. This section outlines the modulation methods adopted by ROHM's short-range wireless lineup.
FSK Frequency Shift Keying This technique utilizes the difference in the amplitude of analog signals to modulate digital signals by switching between low frequency and high frequency in order to represent 0 and 1. Previous Next. This type of modulation requires greater bandwidth, more power. Filtering is very difficult in this modulation.
Frequency modulation FM varies the frequency of the carrier in proportion to the message or data signal while maintaining other parameters constant. It is used in applications like radio, radar, telemetry seismic prospecting, and so on. The efficiency and bandwidths depend on the modulation index and maximum modulating frequency.
In phase modulation , the carrier phase is varied in accordance with the data signal. In this type of modulation, when the phase is changed it also affects the frequency, so this modulation also comes under frequency modulation. If noise enters into a system, it persists and gets carried till the end receiver. Therefore, this drawback can be overcome by the digital modulation technique.
For better quality and efficient communication, the digital modulation technique is employed. The main advantages of digital modulation over analog modulation include permissible power, available bandwidth, and high noise immunity. In digital modulation, a message signal is converted from analog to digital message and then modulated by using a carrier wave.
The carrier wave is keyed or switched on and off to create pulses such that the signal is modulated. Similar to the analog, here the parameters like amplitude, frequency, and phase variation of the carrier wave decides the type of digital modulation. Amplitude shift keying changes the amplitude of the carrier wave based on the baseband signal or message signal, which is in digital format. It is used for low-band requirements and is sensitive to noise. In this way the best form of modulation can be chosen for any given situation.
Each type of modulation has its own advantages and disadvantages, and accordingly they are all used in different radio communications applications. In addition to the three main basic forms of modulation or modulation techniques, there are many variants of each type.
Again these modulation techniques are used in a variety of applications, some for analogue applications, and others for digital applications. Angle modulation is a name given to forms of modulation that are based on altering the angle or phase of a sinusoidal carrier.
Using angle modulation there is no change in the amplitude of the carrier. The two forms of modulation that fall into the angle modulation category are frequency modulation and phase modulation. Both types of angle modulation, namely frequency modulation and phase modulation are linked because frequency is the derivative of phase, i. Each channel gets a certain range usually about 0. Modulation makes it all possible, because it allows us to send voice and music which are essential baseband signals over a bandpass or "Broadband" channel.
A sine wave at one frequency can be separated from a sine wave at another frequency or a cosine wave at the same frequency because the two signals are "orthogonal". There are other sets of signals, such that every signal in the set is orthogonal to every other signal in the set. A simple orthogonal set is time multiplexed division TDM -- only one transmitter is active at any one time.
Other more complicated sets of orthogonal waveforms—Walsh codes and various pseudo-noise codes such as Gold codes and maximum length sequences—are also used in some communication systems. The process of combining these waveforms with data signals is sometimes called "modulation", because it is so very similar to the way modulation combines sine waves with data signals.
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